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Area Forecast Discussion
172 FXUS62 KCHS 240605 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 205 AM EDT WED AUG 24 2016 .SYNOPSIS... High pressure will build from the north tonight, then prevail across the region into the weekend. A cold front could stall over or close to the region early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Tuesday was the 63rd day in a row with temps reaching at 90F at KSAV, by far it`s longest stretch on record of temps at least that high. Tonight: A strong and deep anticyclone centered over the lower MS Valley, with 500 mb heights near 5970 meters, and a 1026 mb high pressure system near the Delmarva and starting to wedge into the inland parts of the southeast will prevail. Drier air above the first mile or two of the troposphere will allow for mostly clear skies far north, partly cloudy skies or becoming partly cloudy most elsewhere. Some late night showers driven by low level convergence could skirt the coastal counties close to or after daybreak Wednesday. Maybe some late night stratus over interior GA with nocturnal cooling and the wet grounds from recent rains. But probably too much mixing in the planetary boundary layer for anything more than ground fog, but we`ll continue to assess the potential for more significant fog due to the earlier rains. Temps will bottom out in the lower and middle 70s most communities, with the exception of some upper 60s in normally cooler rural areas of Berkeley and Dorchester counties, and upper 70s to near 80 on the barrier islands. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... An expansive ridge of high pressure will prevail over the Southeast mid to late week, favoring a dry forecast for most if not all locations. The only exception could be an isolated shower that drifts onshore in Southeast Georgia or well inland where a weak sfc trough develops over the Midlands late week. Otherwise, expect rain- free conditions with near normal temps for a few days. In general, afternoon highs should peak in the upper 80s to lower 90s Wednesday and Thursday, before the mid/upper ridge becomes directly centered over the Southeast and warms temps into the lower/middle 90s on Friday. Overnight lows will range in the upper 60s/lower 70s inland to middle/upper 70s near the coast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... To start this period, deep-layered high pressure should maintain a dry/capped environment supporting temps in the mid 90s and a return of 100F heat index values to much of the forecast area. Similar temps and slightly higher dewpoints/heat index values can be expected Sunday. Meanwhile, a weakening cold front will push into the region late Sunday and will stall over or close to the region early next week. To account for this feature, maintained slight chance pops Sunday and slight chance/chance pops Monday. Tuesday, slight chance/chance pops are limited to far southern counties, although the eventual position of the stationary front and associated POPs remain uncertain. Otherwise, this front could produce Monday/Tuesday temps a couple of degrees lower than those of the weekend, although a significant airmass change appears unlikely. Also of note, medium range guidance solutions regarding possible tropical development differ greatly early next week. Attempts to incorporate any specific tropical scenario into early week forecasts would be based on speculation rather than solid, supportable forecast reasoning. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... VFR will prevail through 06Z Thu. Extended Aviation Outlook: VFR conditions are expected at both CHS and SAV terminals. && .MARINE... Tonight: A 1026 mb high pressure system will be centered over the mid-Atlantic states, with the southern periphery of this feature continuing to build into our area. A fairly modest E-NE gradient between the high and lower pressures in the Bahamas and Caribbean will lead to winds up near 15 or 15-20 kt throughout the night, with slight decrease in speeds in Charleston Harbor late. Seas will be 3 ft within 20 nm and 3-4 ft across AMZ374, with some 5 footers out near 50-60 nm off the coast. Wednesday through Sunday: High pressure will dominate the coastal waters through the weekend, supporting east/northeast winds around 15 kt and gusts occasionally up to 20 kt over Georgia waters. Seas will range between 2-4 feet, although occasional 5 feet seas will push into waters beyond 20 nm this weekend. Small Craft Advisory conditions appear unlikely at this time. Rip currents: Onshore winds and a small long period swell will persist this week, elevating the risk of rip currents late week. There is a chance that the swell could increase in size late this weekend. If this occurs, the chance for rip currents will increase significantly. && .TIDES/COASTAL FLOODING... A long duration of northeast winds will support elevated high tides through late week. Extratropical surge guidance continues to hold tides just below Coastal Flood Advisory levels. There remains a low probability that slightly stronger than expected northeast winds could overcome this gap, pushing early/mid afternoon high tide levels to Coastal Flood Advisory thresholds. && .EQUIPMENT... The Metter NOAA Weather Radio All Hazards station, WWH-25 will be off the air until further notice. The telephone company is investigating the problem. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM...SPR AVIATION...JRL MARINE... TIDES/COASTAL FLOODING... EQUIPMENT...